xref: /src/libexec/ld.elf_so/search.c

/*	$NetBSD: search.c,v 1.27 2020/04/22 23:54:32 joerg Exp $	 */

/*
 * Copyright 1996 Matt Thomas <matt (at) 3am-software.com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by John Polstra.
 * 4. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * Dynamic linker for ELF.
 *
 * John Polstra <jdp (at) polstra.com>.
 */

#include <sys/cdefs.h>
#ifndef lint
__RCSID("$NetBSD: search.c,v 1.27 2020/04/22 23:54:32 joerg Exp $");
#endif /* not lint */

#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <dirent.h>

#include "debug.h"
#include "rtld.h"

/*
 * Data declarations.
 */
static Search_Path    *_rtld_invalid_paths;

static Obj_Entry *_rtld_search_library_path(const char *, size_t,
    const char *, size_t, int);

static Obj_Entry *
_rtld_search_library_path(const char *name, size_t namelen,
    const char *dir, size_t dirlen, int flags)
{
	char pathname[MAXPATHLEN];
	size_t pathnamelen;
	Obj_Entry *obj;
	Search_Path *sp;

	pathnamelen = dirlen + 1 + namelen;
	if (pathnamelen >= sizeof(pathname))
		return NULL;

	for (sp = _rtld_invalid_paths; sp != NULL; sp = sp->sp_next) {
		if (sp->sp_pathlen == pathnamelen &&
		    sp->sp_path[dirlen] == '/' &&
		    !memcmp(name, sp->sp_path + dirlen + 1, namelen) &&
		    !memcmp(dir, sp->sp_path, dirlen)) {
			return NULL;
		}
	}

	memcpy(pathname, dir, dirlen);
	pathname[dirlen] = '/';
	memcpy(pathname + dirlen + 1, name, namelen);
	pathname[pathnamelen] = '\0';

	dbg(("  Trying \"%s\"", pathname));
	obj = _rtld_load_object(pathname, flags);
	if (obj == NULL) {
		Search_Path *path;

		path = NEW(Search_Path);
		path->sp_pathlen = pathnamelen;
		path->sp_path = xstrdup(pathname);
		path->sp_next = _rtld_invalid_paths;
		_rtld_invalid_paths = path;
	}
	return obj;
}

/*
 * Find the library with the given name, and return its full pathname.
 * The returned string is dynamically allocated.  Generates an error
 * message and returns NULL if the library cannot be found.
 *
 * If the second argument is non-NULL, then it refers to an already-
 * loaded shared object, whose library search path will be searched.
 */
Obj_Entry *
_rtld_load_library(const char *name, const Obj_Entry *refobj, int flags)
{
	extern char *__progname;
	char tmperror[512], *tmperrorp;
	Search_Path *sp;
	const char *pathname;
	int namelen;
	Obj_Entry *obj;

	if (strchr(name, '/') != NULL) {	/* Hard coded pathname */
		if (name[0] != '/' && !_rtld_trust) {
			_rtld_error(
			"absolute pathname required for shared object \"%s\"",
			    name);
			return NULL;
		}
		pathname = name;
		goto found;
	}
	dbg((" Searching for \"%s\" (%p)", name, refobj));

	tmperrorp = dlerror();
	if (tmperrorp != NULL) {
		strlcpy(tmperror, tmperrorp, sizeof(tmperror));
		tmperrorp = tmperror;
	}

	namelen = strlen(name);

	for (sp = _rtld_paths; sp != NULL; sp = sp->sp_next)
		if ((obj = _rtld_search_library_path(name, namelen,
		    sp->sp_path, sp->sp_pathlen, flags)) != NULL)
			goto pathfound;

	if (refobj != NULL)
		for (sp = refobj->rpaths; sp != NULL; sp = sp->sp_next)
			if ((obj = _rtld_search_library_path(name,
			    namelen, sp->sp_path, sp->sp_pathlen, flags)) != NULL)
				goto pathfound;

	for (sp = _rtld_default_paths; sp != NULL; sp = sp->sp_next)
		if ((obj = _rtld_search_library_path(name, namelen,
		    sp->sp_path, sp->sp_pathlen, flags)) != NULL)
			goto pathfound;

	_rtld_error("%s: Shared object \"%s\" not found",
	    refobj ? refobj->path : __progname, name);
	return NULL;

pathfound:
	/*
	 * The library has been found, but it couldn't be loaded for some
	 * reason.
	 */
	if (obj == OBJ_ERR)
		return NULL;
	/*
	 * Successfully found a library; restore the dlerror state as it was
	 * before _rtld_load_library() was called (any failed call to
	 * _rtld_search_library_path() will set the dlerror state, but if the
	 * library was eventually found, then the error state should not
	 * change.
	 */
	if (tmperrorp)
		_rtld_error("%s", tmperror);
	else
		(void)dlerror();
	return obj;

found:
	obj = _rtld_load_object(pathname, flags);
	if (obj == OBJ_ERR)
		return NULL;

	return obj;
}